We have demonstrated the existence of two previously undelineated collagen chains (termed alpha A and alpha B) which occur in native collagen molecules of identical solubility behavior, and in an apparent 1:2 ratio. This study is designed to provide further structural information on the individual alpha A and alpha B chains by isolation of constituent cyanogen bromide peptides, followed by estimations of molecular weights, amino acid compositions and glycosylation. In addition, we are pursuing studies designed to confirm the postulated composition of the native molecule as being alpha A (alpha B)2 and further immunohistologic studies of various human tissues to define the distribution of this new human collagen.